1. Field of the Invention
The present invention relates to a hard disc device having a normal density memory region and a low density memory region.
2. Description of Related Art
Generally in a hard disc device, characteristics of a magnetic disk and a head deteriorate as ambient temperature becomes lower than a certain level. If this happens, data may not be successfully stored and the stored data may not be successfully read out. In the worst case, data may be destroyed. In order to avoid this problem, the following counter measures have been proposed. (1) Data storing operation is prohibited when the ambient temperature becomes lower than a predetermined level. (2) Data are read out immediately after the data are stored to check whether the data are successfully stored, and if some deficiencies are found, storing and reading-out are repeated until such operations succeed. (3) The magnetic disc having a low memory density is prepared for operation at a low temperature.
As to the counter measure (1), the hard disk cannot be used until the ambient temperature becomes higher than the predetermined level. As to (2), the storing operation may not succeed for a long period of time, and efficiency of the hard disk device may be greatly sacrificed. As to (3), a capacity of the hard disk is reduced although the storing operation is carried out at a low temperature.
JP-A-58-147802 proposes a magnetic disk that has a low memory density at its outer circumference to cope with expansion of the disk according to a temperature rise. This proposal, however, has nothing to do with above-mentioned problems at a low temperature.